The use of chlorine dioxide in the treatment of water for disinfection and removal of oxidizable species, such as carbonaceous and sulphurous materials, is well known and is known to have advantages over the use of chlorine. For example, chlorine dioxide avoids the formation of chlorinated end products which are mutagenic and chlorine dioxide is capable of eliminating chlorinated phenolic tastes. Relatively small quantities of chlorine dioxide are required in such use, typically 500 to 2000 lbs/day in a municipal sewage treatment plant of a medium-sized community.
Usually, chlorine dioxide is formed in a reaction zone from chlorine dioxide-generating reactants in an aqueous acid reaction medium and is removed from the reaction zone in a gaseous product stream in which the partial pressure of chlorine dioxide is maintained sufficiently low to prevent decomposition of the chlorine dioxide. The chlorine dioxide gas then is dissolved in water for later use or directly in the water to be treated by the chlorine dioxide. In addition to producing gaseous products of reaction, which must be processed to an aqueous solution form, previous efforts at producing chlorine dioxide in a small compact unit with high yield, short residence time and high production rates have failed, mainly as a result of slow or incomplete reaction.